The main goals of this research are to test the ability of dietary sulforaphane (SFN) to prevent spontaneous, or oncogene-induced, breast cancer, and thereby to establish a tractable system for novel mechanistic studies of SFN-mediated breast cancer suppression. SFN is a dietary isothiocyanate derived from a precursor compound (glucoraphanin) during consumption of cruciferous vegetables such as broccoli, a particularly rich source of the SFN precursor. Consistent with the inverse relationship between cruciferous vegetable intake and breast cancer risk identified in some observational studies, SFN has potent anticancer activity in experimental breast cancer models. Specifically, SFN protects against rodent breast neoplasia induced by carcinogen treatment, most likely as a consequence of Phase II enzyme induction and resultant acceleration of carcinogen deactivation. Recently however, a novel activity has been identified for SFN as an epigenetic modulator through inhibition of histone deacetylase (HDAC) activity. Strikingly, SFN has been shown to alter histone acetylation status both in vitro and in vivo in mice and humans. Here we propose to study SFN using a carcinogen-independent or spontaneous breast cancer model in which estrogen receptor (ER) -negative breast neoplasia is driven by oncogene overexpression. This widely used mouse model should provide a useful experimental system in which to ultimately evaluate the importance of SFN-mediated HDAC inhibition. SFN will be delivered in the form of broccoli sprouts, an exceptionally rich source of the SFN precursor. This provides maximal translational relevance since ongoing NCI-funded trials are testing broccoli sprout SFN in patients with breast and prostate intraepithelial neoplasia. The goals of the research proposed herein are two- fold. Firstly, we will test the effect of dietary SFN on tumor formation, multiplicty, growth rate and metastasis. Secondly, we will examine SFN-mediated modulation of biological endpoints in mouse mammary tissues, using normal and precancerous breast tissues and breast carcinomas. Assays will include: HDAC activity and histone acetylation status, Phase II enzyme expression, proliferation and apoptosis. Additionally, we will compare ER expression in tumors from control and SFN-treated mice. These pilot studies will lay the foundation for future R01-scale investigations to establish causal links between observed changes and SFN- mediated tumor protection, and for investigating the utility of SFN for epigenetically restoring sensitivity of ER- negative cancers to endocrine therapy. We anticipate that data obtained from these studies will be extremely important for informing biomarker selection for clinical studies of SFN for breast cancer prophylaxis. By using broccoli sprouts we emphasize a whole-food approach to cancer prevention which may be pertinent in developing evidence-based health recommendations that could significantly reduce the burden of breast cancer. Our proposal is thus highly responsive to several areas of interest defined by PAR-11-079.